The present invention relates to methods of filling a syringe that reduce wastage of a liquid used to fill the syringe, and of damaged hypodermic needles.
Medical hypodermic syringes are typically filled by attaching a hypodermic needle to the body of a syringe, penetrating a sealing septum of a medicinal liquid supply vial and withdrawing the liquid stored therein into the body of the syringe. Alternatively, the liquid to be loaded is supplied in a glass vial, and the heat-sealed neck is removed before inserting the needle of the syringe to extract the liquid.
The charging or loading process, however, often results in wastage of some of the liquid. This occurs most frequently when a residual volume remains in the supply vial from which the liquid has been extracted. The excess liquid that remains in the vial after extraction of the selected pharmaceutical dose is included by both practical necessity and mandated by regulation of pharmaceutical products. It serves to ensure that the full amount of the prescribed dose of a medication is received into the syringe and thereby administered to a patient.
A second source of waste of liquid during the standard method of filling a syringe arises out of the common technique of eliminating air both from the body of a liquid-charged syringe and the lumen of the attached hypodermic needle. This particular step in the process cannot be avoided, as to do so would introduce the risk of injecting air into the blood stream and creating an air embolism, with potentially fatal consequences. The method that is commonly adopted, therefore, is to slightly depress the plunger of the syringe to eject small volume of liquid, simultaneously forcing out any entrapped air. To ensure that all gas bubbles are dislodged from the interior walls of the syringe barrel, the syringe is sharply tapped, an action that may also dislodge a volume of liquid from the needle tip.
While small in themselves, the accumulated losses of liquid may become quite considerable. When the liquid is a pharmaceutical preparation, the economic loss of a drug may be significant. The possibility of accidental contamination of the syringe user, a bystander or the patient by dislodged liquid from the needle tip is another potentially dangerous consequence of the syringe filling technique most commonly practiced.
A further disadvantage of the standard manual procedure for charging a medical hypodermic syringe is that frequently a small gauge needle is required for the subsequent inoculation into an animal or human. Many liquid pharmaceutical products however are supplied in vials sealed by a flexible septum. It is intended that penetrating this septum with a hypodermic needle and withdrawing the liquid from the vial into body of the syringe will charge the syringe. The thickness and density of the sealing septum of a liquid supply vial can easily result in the bending or blunting of a piercing hypodermic needle. This, of course, renders it useless for the subsequent penetration into the skin of the recipient individual. Since a replacement needle may be necessary, needle costs will double and become an additional burden on medical facilities already under financial constraint.
Several apparatus of varying degrees of complexity have been devised that will charge a multiplicity of syringes, or the automatic charging of a single syringe. None of these devices, however, overcomes the need to further dislodge any introduced gas bubbles. These devices, therefore, still result in some losses of the liquid.
What is needed, therefore, are methods of filling syringes that avoid the wastage of the liquid that can occur during the filling procedure itself. There is also a need to avoid the necessity of replacing the hypodermic syringe needle that was used in the process of charging the syringe with a liquid, with a fresh needle immediately prior to transdermal injection of the liquid. What is also needed is a method of charging multiple syringes from a single liquid supply vial so that there is no repetitive wastage of the liquid when each syringe is filled, and so that there is a single penetration of the sealing septum of the liquid supply vial. What is also required is a simple manual method of charging multiple syringes with a reduced likelihood of entrapping gas bubbles.
The present invention solves the problems described above by providing simple manual methods of filling a syringe, wherein the wastage of liquid is reduced, and the need to replace a damaged delivery needle is avoided.
Charging a syringe with a liquid from a supply vial leaves behind a residual unusable, and therefore wasted, volume of the liquid in the supply vial. Further loss of liquid occurs when eliminating entrapped air from within the syringe and the attached needle. Wastage also occurs if a hypodermic needle becomes deformed or otherwise damaged during the piercing of the sealing septum of a liquid supply vial.
The methods of the present invention therefore comprise the filling of a distributing syringe with a liquid from a supply vial, placing the distributing syringe in communication with at least one receiving syringe, and transferring the liquid to the receiving syringe whereupon the receiving syringe is filled. Communication between the distributing syringe and the receiving syringe is preferably achieved by inserting the hypodermic needle of the distributing syringe into the nozzle of the receiving syringe. A multiplicity of syringes may be filled from one distributing syringe by repeating the steps of needle insertion and liquid transfer. Depressing the plunger of the delivery system and filling the receiving syringe to a predetermined volume eliminates entrapped air within the receiving syringes. A delivery needle is attached to the receiving syringe, which is then used to administer the liquid to an animal or human.
The method of the present invention allows the charging of multiple receiving syringes from a single distributing syringe without the necessity of reloading the distributing syringe.
The method of the present invention avoids the use of a fresh supply vial for the charging of each receiving syringe, thereby lessening the losses of excess volumes of the liquid that remain in the supply vials.
The method of the present invention also limits the penetration of a sealing septum of a supply vial to the needle attached to the distributing syringe. Accordingly, it is an object of the present invention to provide a method of filling a syringe whereby wastage of a liquid is minimized and replacement needles are avoided.
It is an object of the present invention to provide a method of loading a distributing syringe with a liquid, filling at least one receiving syringe with liquid transferred from the distributing syringe so that wastage of a residual liquid in a supply vial is minimized.
It also is an object the present invention to provide a method of filling at least one receiving syringe without damaging and wasting small gauge hypodermic needles by penetration through a sealing septum of a liquid supply vial.
It yet another object of the present invention to provide a manual method of filling at least one receiving syringe from a distributing syringe so as to avoid residual gas bubbles in the receiving syringe.
These and other features, objects and advantages of the in invention and preferred embodiments of the present invention will become apparent from the detailed description that follows.